Acute mountain sickness when travelling

The higher you go, the less oxygen there is in the air. The body adapts by breathing more, but this acclimatisation takes several days. If you go up faster, the body lacks oxygen: the first symptoms appear 6 to 10 hours after the ascent.

The risk starts at around 2500 metres. Above 4500 metres, up to half of travellers are affected. Being fit does not protect you: the risk depends mainly on how fast you go up and the altitude at which you sleep.

In severe forms, fluid builds up in the brain or the lungs: this is high-altitude oedema. It is life-threatening.

A stay above 2500 metres is not recommended, or requires medical advice, if you have:

• a serious lung disease, for example needing oxygen at home;
• poorly controlled heart disease, or a heart attack in the last 3 months;
• had a stroke in the last 3 months;
• poorly controlled epilepsy;
• sickle cell disease, an inherited disease of the red blood cells;
• a high-risk pregnancy.

Other conditions also require medical advice: anaemia, migraine, kidney stones, Raynaud's disease, among others.

Above 2500 metres:

• do not sleep more than 300 to 500 metres higher than the night before;
• take an extra rest day for every 1000 metres gained;
• go higher during the day if you wish, then come back down to sleep lower.

Many organised tours go up too fast: check the itinerary before booking. Drink more than usual (dark urine means you need to drink more) and eat plenty of carbohydrates (pasta, rice, bread). Avoid alcohol, tobacco and sleeping pills.

Acetazolamide makes you breathe a little more, especially at night, which helps acclimatisation. It is useful if a slow ascent is impossible, or if you have had altitude sickness before. It does not replace a slow ascent.

You start it the day before going above 2500 metres. The dose and duration are set at your consultation, according to the Swiss experts' guidelines. Do a 3-day trial before you leave. Tingling in the fingers and a metallic taste are common and harmless.

It is prescription-only. Mention any allergy to sulphonamides. If you cannot take it, dexamethasone, a cortisone-type medicine, is an alternative: if it is indicated, we prescribe it at your consultation.

Give each of these symptoms a score from 0 to 3: headache, nausea or loss of appetite, dizziness, tiredness (0 = none, 3 = severe and disabling). Add them up:

A medicine can help with nausea: ask for it at your consultation. Only start going up again once all the symptoms have gone.

Go down immediately, even at night, if there is:

1. confusion, a change in behaviour, unusual drowsiness;
2. unsteady walking, like a drunk person;
3. breathlessness at rest, cough, noisy breathing;
4. a headache that does not respond to medicines, with vomiting.

Go down at least 500 to 1000 metres, until the symptoms improve. Give oxygen if you have it. Call the local emergency services and your travel insurance.

In Switzerland, emergencies: 144. Abroad: the local emergency number.

Breathlessness or a cough that persists after you return? See a doctor.